Ethylene fluoro-containing copolymers

Abstract

Ethylene fluoro-containing copolymers of the ECTFE and ETFE type, optionally in the presence of a third comonomer in amount comprised between 0.1 and 10% by moles, having a viscosity between 102 and 105 Pa.sec with shear rates of 1 sec-1 measured at the temperature of about 30° C. higher than the second melting temperature, and having a rheologic curve in the diagram shear viscosity/shear-rate with a slope higher than 200, calculated as ratio between the viscosity in Pa.sec and the shear-rate in sec-1 in the shear-rate range comprised between 1 and 10 sec-1, and having a processability zone with shear-rate values higher than 10 s-1.

What is claimed is:  
     
       1. ECTFE and ETFE ethylene fluoro-containing copolymers, optionally in the presence of one or more comonomers, the total amount of which is comprised between 0.1 and 10% by moles, having a viscosity between 10 2  and 10 5  Pa.sec with shear rates of 1 sec −1  measured at the temperature of about 30°-50° C. higher than the second melting temperature, and having a rheologic curve in the diagram shear viscosity/shear-rate having a slope higher than 200, calculated as ratio between the viscosity in Pa.sec and the shear-rate in sec −1  in the shear-rate range comprised between 1 and 10 sec −1 , said curve having a processability zone with shear-rate values higher than 10 s −1 . 
     
     
       2. ECTFE and ETFE ethylene fluoro-containing copolymers, according to claim  1 , wherein the copolymers show a molecular weight distribution of bimodal type, i.e. contain a polymeric fraction with low molecular weight having a viscosity comprised between 1 and 5.10 3  Pa.sec, said low molecular weight fraction being comprised between 5 and 60% by weight, the remaining part having a higher molecular weight and being in amounts corresponding to the complement to 100% by weight. 
     
     
       3. ECTFE and ETFE ethylene fluoro-containing copolymers, according to claim  2 , wherein the low molecular weights fraction is comprised between 30 and 55% by weight. 
     
     
       4. A method of making pipes, sheets and cables of ECTFE and ETFE ethylene fluoro-containing copolymers, according to claim  1 , comprising forming said pipes, sheets and cables with said copolymer. 
     
     
       5. A method for making flexible pipes of ECTFE and ETFE ethylene fluoro-containing copolymers, according to claim  4 . 
     
     
       6. A method for manufacturing flexible pipe for petroleum transport at deep sea comprising extruding a mixture of ECTFE and ETFE and one or more modifying comonomers selected from the group consisting of fluoro-containing vinylic comonomer, comonomers of the formula R—CH═CH 21 , wherein R is a perfluoroalkyl or a perfluoroalkyloxy-perfluoroalkyl and fluorodioxoles, wherein said mixture has a viscosity between 10 2  and 10 5  Pa.sec with shear rates of 1 sec −1  measured at the temperature of about 30°-50° C. higher than the second melting temperature, and having a rheologic curve in the diagram shear viscosity/shear-rate having a slope higher than 200, calculated as ratio between the viscosity in Pa.sec and the shear-rate in sec −1  in the shear-rate range comprised between 1 and 10 sec −1 , said curve having a processability zone with shear-rate values higher than 10 s −1 .